Many communication systems utilize blind detection to reduce overhead. Without blind detection, a communication system uses additional signaling to setup and coordinate transmissions. With blind detection, no additional signaling is necessary to setup a transmission of a frame or to indicate properties of the transmission to a receiver, such as the type of modulation and coding used in the transmission. The systems may employ a setup of generic transmission properties before any frame is transmitted. Blind detection receivers often feature powerful computation capabilities sufficient to try multiple possibilities for the properties of a transmission when detecting and decoding.
Many communication systems, particularly wireless systems, use some form of retransmissions to enhance performance, referred to as HARQ. In a first transmission, a transmitter transmits encoded bits of data toward a receiver. Ideally, the receiver is able to detect and decode the transmission and typically sends an acknowledgment of receipt to the transmitter. When the receiver is unable to detect and decode a transmission, in HARQ systems, the transmitter re-transmits at least a portion of the encoded bits. The receiver then combines the re-transmission and the first transmission for decoding. Combining two or more transmissions can be achieved by a variety of techniques, including chase combining or incremental redundancy, among others.
Blind detection and HARQ are examples of techniques that allow certain communication systems to improve system performance and efficiency.